1. Field of the Invention
The present invention relates to the field of machining workpieces made of metal, such as steel, and, more particularly, to an apparatus to form a workpiece.
2. Description of the Related Art
The machining of a workpiece can include any process such as cutting, pressing, drawing and shaping.
Pot-shaped components can include a bottom, a container wall and a drawn edge. Such a component is often used as a spring cup for accommodating the ends of a coil spring. They are used widely in the automotive industry in particular.
High-strength steels are problematic in the production of such spring cups. Although these have the advantage that they have extremely high tensile strengths, such steels are relatively brittle and prone to tearing. Therefore steels of lesser thickness and lower weight may be used. This occurs particularly during deformation at high stress transition zones. The tearing occurs in particular in the transition regions between the cup bottom and cup wall and between the cup wall and drawn edge.
DE 102 54 103 B3 describes a deep-drawing tool for deep drawing of formed parts. This includes an annular clamping device for clamping a blank. The clamping device encloses a space in which a bottom and a former body are movable in the drawing direction. These two may have different speeds, which should lead to higher forming precision.
DE 27 27 174 C2 describes a method and an apparatus for deep drawing of an aluminium container. In this case, two parts are mutually movable, namely a punch and a die. The speed of the upwardly moving punch can be greater than the speed of downwardly moving die. A high drawing ratio is achieved in this way.
DE 10 2007 050 581 A1 discloses a method for influencing the sheet thickness progression in deep drawing of hollow bodies. This involves multiple cambering (deformation) and back cambering (reforming) of a workpiece. During the reforming phase, the relative velocity between the punch and the die is increased relative to the increased rate during the deforming phase. The punch performs a movement against the deforming phase during the reforming phase. The speeds of the punch during the phases are unequal.
What is needed in the art is an apparatus and method so that high-strength steels can be formed without leading to any tearing in the edge regions and drawn to a greater depth than could be achieved before.